This invention generally relates to adjusting devices for cutting tools and is specifically concerned with a device for adjusting the position of the cutting edge of an insert mounted onto the body of a tool such as a milling cutter.
Devices for adjusting the position of cutting inserts in milling cutters and other tools are known in the prior art. However, before such adjusting devices are described, a brief description of the mechanical context of such devices will be given.
Milling cutters have a generally cylindrical tool body. A plurality of cutting inserts are mounted around the periphery of the body of the milling cutter in recesses known as "pockets" that conform to the shape of two of the sides of the inserts. Each insert is secured into its respective pocket by means of a clamping screw which extends through a centrally-located hole in the insert. While pockets and clamping screws provide a secure mount for the inserts during a cutting operation, they do not, unfortunately, provide the system operator with any means for making fine adjustments in the position of the cutting edges of the inserts mounted around the periphery of the milling cutter. This is unfortunate, since even small misalignments between the edges of the cutting inserts on the order of 0.001 inch can result in tool marks in the workpiece known in the art as "tracking." Even if the pockets were perfectly machined to the desired dimension, the inserts themselves can easily vary in size 0.001 of an inch or more due to manufacturing tolerances or uneven wear during use.
To solve this problem, devices for making small adjustments in the position of the cutting inserts in such tools were developed in the prior art. In one of the most common designs, one of the walls of the insert-receiving pockets in the tool body is replaced with a wedge-shaped member that is slidably mounted onto the body of the milling cutter or other tool by means of one or more adjustment screws. The screws are turned in order to slide the wedge-shaped body in a direction which can move the cutting edge of the insert either upwardly or downwardly with respect to the cutting edges of the other inserts mounted around the body of the milling cutter.
While such a prior art devices are capable of aligning the cutting edges of the inserts to an extent to where tracking is substantially or completely eliminated, the applicants have observed a number of shortcomings associated with such devices. For example, the metal-to-metal contact between the wedge-shaped element and the body of the milling cutter often creates, on a microscopic level, an irregular sticking friction (known as "stiction" in the art) which results in irregular movement of the sliding wedge element as the adjustment screw is turned. Such stiction coupled with the fact that even a partial turn of the adjusting screw moves the wedge-shaped element a relatively large distance on a microscopic level often causes the system operator to overshoot his intended positioning goal (which may be as small as 0.0005 inches). The resulting overshooting of the position goal in turn requires the system operator to loosen the adjustment screw and start over, thus creating an undesirable amount of unproductive downtime for the milling cutter or other tool. Another shortcoming of such a design is that it requires the manufacture and assembly of additional precision parts onto the body of the milling cutter. This of course results in higher manufacturing costs. Finally, it is possible for the adjustment screws used in such devices to loosen slightly from the vibrations associated with the machining operation, thus causing the cutting edge of the insert to shift out of position.
Clearly there is a need for a device for making fine adjustments to the position of cutting inserts mounted around a milling cutter or other tool in order to eliminate undesirable tracking in the workpiece which is easier and faster to use than prior art adjusting devices. Ideally, such an adjusting device would require the manufacture and assembly of fewer precision parts so as to minimize the cost of the resulting adjustable milling cutter or other tool, and would resist becoming loosened from the shock and vibration caused by the machining operation. Finally, it would be desirable if such an adjusting device could be easily installed onto existing milling cutters and other types of cutting tools.